It is common for off-road vehicles to drive through a body of water and this is often referred to as a wading event. Driver caution and judgement is required when navigating a vehicle through a body of water at wading depth. This is because a vehicle driver does not generally know the depth of water the vehicle is about to enter or the nature of the terrain below the water surface. This is particularly so in low visibility conditions (dirty water, low-light, heavy rain, fog). It is recommended that a survey of the terrain is taken by wading through water on foot, but factors such as, the variability of the terrain; low visibility conditions; inconvenience to the driver; and driver impatience may result in a driver attempting to traverse water without knowledge of the water depth and therefore without being able to taking appropriate precautions.
The present applicant has submitted a series of patent applications relating to the detection of a body of water using one or more sensors mounted externally on the vehicle. Such sensors include: ultrasonic transducer sensors, capacitative sensors, resistive sensors and hydrostatic sensors capable of issuing data to a control system indicative of the presence of water about the sensor and/or a range to the surface of the water about the vehicle and/or the depth of water about the vehicle.
For example, in PCT/EP2011/072997 (incorporated herein by reference), also to the present applicant, a system is disclosed that upon detecting wading by means of a sensor, (such as that described in PCT/EP2011/072998 (incorporated herein by reference) and PCT/EP2011/072999 (incorporated herein by reference)), a downwardly facing ultrasound transducer is used to estimate a wading depth (D) of the water in which at least a portion of the vehicle is known to be disposed.
The data obtained by such sensors is intended to inform and assist a driver of the vehicle as the driver navigates the vehicle into, through and out of a body of water. In PCT/EP2011/072992 (incorporated herein by reference), PCT/EP2011/072994 (incorporated herein by reference), and PCT/EP2011/072996 (incorporated herein by reference), to the present applicant, a human machine interface (HMI) for displaying information relating to maximum wading depth, water level relative to a vehicle body, and an advisory speed for the vehicle given the conditions are respectively disclosed.
It has been recognised by the present applicant however that data obtained by sensors mounted to a vehicle may lead to a mis-interpretation or mis-representation of the true vehicle scenario. For example, a resistive or capactitive sensor may issue data indicative of the vehicle being disposed in a body of water and such data may be used to activate an in-cabin HMI to alert the driver to the vehicle being in a wading event. In fact, the vehicle may have been travelling along an un-even off-road surface and the water detected was merely a localised puddle in a rut or a splash from a puddle.
In a further example, a submersion ultrasonic transducer sensor may issue data relating to its settling time that is indicative of the vehicle being disposed in a body of water; and a surface ranging ultrasonic transducer sensor mounted to a vehicle upperbody may issue data at the same time relating to the presence of a surface intermediate the surface ranging sensor position and a ground level. An interpretation of this data is that water is disposed about the vehicle at the height of the detected surface. However, the detected surface may in fact be a bush positioned between the ground level and the surface ranging ultrasonic transducer sensor and above the water level. Activating an HMI on the basis of such an interpretation and/or presenting such depth information to the driver on an HMI may be distracting and as such disadvantageous.
There are many and various scenarios in which the data obtained from vehicle body mounted wading sensors can be mis-interpreted and could lead to an inappropriate, inaccurate, unhelpful and/or unexpected activation or termination of an HMI-apparatus.
The present invention seeks to provide a further improvement for land-based vehicles, which may travel through water, by providing an in-vehicle HMI (human-machine-interface) apparatus for providing information about wading. More specifically, but not exclusively, to a control system, an algorithm and a method for determining, inter alia: when to activate the HMI apparatus, when to deactivate the HMI apparatus and/or what information should be displayed by the HMI apparatus.